Circuit breaker



Jan. 2, 1940. L.. s. wALLE CIRCUIT BREAKER Filed Jan. 28, 1958 m, im wwwnsd FM 11u His Attorney.

Patented Jan. 2, 1940 CIRCUIT BREAKER Ludwig S. Walle, Lansdowne, Pa.,assignor to General Electric Company, a corporation New York ApplicationJanuary 28, 1938, Serial No. 188,275

7 Claims.

My invention relates to circuit breakers, more particularly to circuitbreakers of the type known as branch-circuit circuit breakers whichprovide the protective features characteristic'of a fuse as well as theadditional advantages of a manually operated switch, and has for anobject the provision of a simple, reliable and inexpensive circuitbreaker of this character.

Heretofore, branch circuit breakers have been provided with a thermalrelease arranged to trip the circuit breaker upon the occurrenceof anoverload, and with a manually operable handle for opening and closingthe circuit independently of the thermal release. However, much is yet15 to be desired in such circuit breakers hitherto proposed to replacefuses because of the fact that the arc has been extinguished by means ofmagnetic blowouts and the like with resulting flame and arc gases.Inasmuch as branch circuit breakers as applied to panel-boards for theprotection of lighting circuits, are called upon to interrupt currentsof very considerable magnitude, as high as 5,000 amperes or more, whenthe breaker carries out the shortl circuit protective 25 functions of afuse, it will be apparent that a considerable quantity of arc gases aregenerated and that the flame of the arc is quite appreciable; these twofeatures being undesirable for circuit breakers for household use.Furthermore, since 30 the fuses which have hitherto been used accomplishthis interruption of the circuit without spurts of flame, and withoutloud popping accompanying the interruption of an overload current ofhigh magnitude, a satisfactory circuit 35 breaker should also possessthese advantages.

In carrying out4 my invention in one form thereof, I provide a circuitbreaker which is capable of interrupting overload currents of largemagnitude at lighting circuit voltages without 40 the emission of nameor arc gases, and without noise, by enclosing the contacts in a sealedsteel chamber of restricted volume. More specifically, I provide amechanism for opening and closing the contacts with a snap action inresponse to 45 movement of an operating handle and for opening with asnaplacticn the contacts in response to overload current. The contactsmove within the sealed metallic chamber s o that when an arc is drawnbetween the separating contacts 50 the gas pressure within the chamberincreases quite rapidly. This pressure may be of the order of 1000pounds per square inch. The resistance of the arc increases rapidly withpressure so that as the pressure is built up the re- 55 sistance becomesso great that the arc can no longer exist, and it is extinguished.

For a more complete understanding of my invention, reference shouldfnowbe had to the accompanying drawing wherein I have shown diagrammaticallyin Fig. 1 a side view partly in section of a circuit breaker embodyingmy invention; Fig. 2 shows the parts of the circuit breaker of Fig. 1just before the contacts are closed, while Figs. 3 and 4, illustrate animproved form of a circuit breaker embodying my invention.

Referring now to Fig. 1, I have shown my invention in one form asapplied to a branch circuit breaker suitable for lighting circuitsindicated by the conductors I0 and II. The circuit breaker, mounted onan insulating base I2, comprises a frame I3 for the operating mechanism,a bi-metallic thermal element I4 and an arc interrupter I5. The frame I3has an upturned end I6 from which is pivotally supported at II anloperating member I8 provided with an operating handle I9. The operatingmember I8 has an extension 2l] to which is rigidly secured a rivet orprojection 2| arranged to cooperate with notches 22 provided in a pairof parallel L-shaped links 26 between which the member I8 moves. Onepair of adjacent ends 29 of the parallel links 26 are pivotally securedat 3l) to the movable contact member 3I of the arc interrupter I5. Theother ends 33 of the links 26 areprovided with projections 34 which areengaged by adjacent ends of a pair of springs 31 which embrace the links26. The other ends of the springs are secured to inwardly projectingends 38 of the frame I3. It will be observed that the circuitrepresented by the conductors I0 and II may be traced from conductors IIthrough the branch circuit breaker by con-ductor 40, thermal element I4,flexible conductor 42, movable contact member 3I,l stationary contactmember 43 provided in the arc interrupter or compression chamber I5 andby conductor 44 to the conductor I0 The contact members 3| and 43 areconstructed of an arc resistant material, for example silver molybdenum,but other arc resistant materials may of course be used.

The operating mechanism of the branch circuit breaker is trip free; thatis to say, the operating handle I9, even though operated, cannotmaintain a closed circuit if a current exists' of sufficient magnitudeto open the breaker. For

example, in theoperation of my invention it will be observed that thecircuit breaker is normally closed after it has opened in response to apredetermined maximum current, the parts then being in the relativepositions shown in Fig. 1, by moving the operating handle I9 downwardly,whereby the operating 'member I8 is rotated in a clockwise directionaround itspivot Il to bring its projection 2I into engagement with thenotch 22 in the links 26 and thus move the links 26 a slight amount in aclockwise direction and also bodily toward the left. When the handlev I9strikes the end of the frame 38 the movable parts are inthe positionsshown in Fig. 2. A projection 48 extending from the links 26 is movedfrom the position shown in Fig. 1 toward the left past a latch 49carried by the thermal element I4. The latch may of course be operatedby means other than a thermal element. At this time the movable contact3| has not engaged the stationary contact 43 to close the contact. Assoon, however, as the operating handle I9 is released the springs 31rotate the links 26 about the projection 48 to operate the movablecontact 3| into engagement with the contact 43 with a snap action, thusclosing a circuit through the breaker. The springs 31 expend only a partof their energy in operating the contact 3| to the closed position. Theremaining energy is at all times available for operating with a snapaction the contact 3| to the open circuit position in response tooverload or short circuit current. The floating links 26 in the final orclosed circuit position are free of the operating handle. The links 26as they free themselves from the handle I9 impart to the handle throughthe projection 2| an impulse which returns the handle towards the oil`position. As shown in Fig. 1, the handle is retained in an intermediateposition by the engagement of the end 20 of the handle with the leafspring carried on the frame. By moving the handle I9 from thisintermediate position in a counterclockwise direction, asviewed in Figs.1 and 2, a projection I6a carried by the operating member I6 operativelyengages the thermal element I4 to move it to release the latchingprojection 46. The springs 31 thereupon operate the movable contact 3|with a snap action to the open circuit position. It will be understoodthat the movable contact 3| may also be moved to the open position bymoving the handle I9 downward whereby the pin 2| moves the floatingmember 26 about the projection 48 as a pivot to the open position shownin Fig. 2.

Assuming now that an overload occurs on the circuit represented by theconductors I0 and II, the thermal element I4 is flexed in a clockwisedirection to release the latching member 49 from the latching projection46. 'Ihe springs 31 thereupon cause the movable contact 3| to movetoward the right as viewed in Fig. l with a snap action to the opencircuit position shown in Fig. l'. As the movable contact 3| leaves thestationary contact 43, an arc is drawn between them. 'I'he arcinterrupter I6 comprises a steel cylinder 56 within whichI a pair ofkerosene-free fiber bushings BVI and 62 extend. I have found thatkerosene-free fiber oran equivalent material is essential to theoperation of my invention and deem its use in the arc chamber animportant part of my invention. The steel or metallic cylinder and theinsulating members are so arranged as to provide a sealed chamber ofrelatively small volume, such that the arc causes a rapid increase inair pressure in the chamber, thehigh air pressure exerting an ropeningforce on the movable contact; This-increase in pressure is due to theheating by the high temperature of the arc ofthe air within the chamber.The rise in pressure may be further accentuated by the heating of othergaseous fluids produced by the `action of the arc on the air and thematerials within the cylinder.

In order to-produce a strong and rigid construction of'the arc chamber,the bushings 5I andl 62 are inserted into the ends of the steelcylinder. The ends ofthe cylinder are then swaged lover the relativelynarrow peripheral extensions provided on the bushings. The steelcylinder 60 isin turn enclosed in a casing 6|)v cessive operations ofthe circuit breaker.

of insulating material. The stationary contact member 43 has screwthreads 6I provided at one end arranged to cooperate with a threadedmember 62 forming apart of the conductor 44. The insulating bushing 5Ipermits a reciprocal longitudinal movement of the movable contact member3|, one end of which is always located in the chamber and the other endof which is always located outside of the chamber.

A leather sealing washer 66 is provided around the movable contactmember 3|, the washer being provided with an inwardly projectinglcylindrical extension 66. Since a certain amount -of metal vapor isproduced when the circuit breaker interrupts a current of largemagnitude, it is necessary to prevent this metal vapor from collectingon the movable contact member 3| where it may harden and interfere withsuc- The leather washer with its inwardly extending projection tends toprevent this collection of the metallic vapor because of its wipingaction on the movable contact member 3| and furthermore assists inmaintaining a substantially air-tight connection around the movablecontact member 3| by its cooperation with the contact member and thewalls of the chamber At the same time the leather washer provides forsnap movement of the movable contact by the spring means by oiering onlyrelatively slight friction to such movement.

As I have stated, when an arc is drawn between the contacts 3| and 43,the air pressure within the chamber of the arc interrupter increasesrapidly. 'I'he potential drop across the arc is not entirely dependenton the rise in pressure inasmuch as the cross sectional area of an arcis approximately proportional to the current. It is believed that thearc potential drop is approximately proportional to the inverse squareroot of the current. lThis characteristic of the arc, in addition to therise in pressure in the chamber, causes a quick interruption oi thecircuit. Furthermore, since the rise in pressure depends upon themagnitude of the current interrupted, it will be seen that the greaterthe overload current the more quickly will the pres- VSure rise to apoint where the arc resistance becomes so great that the arc can nolonger exist.

Obviously, the pressure within the chamber also- 0f course, it will beunderstood that in order to reclose the circuit breaker it is onlynecessary to repeat the operations described in connection with Figs. 1and 2.

In the modiiled form of my invention, shown in Figs. 3 and 4, I haveprovided Ia rotatable bridging contact 61 which is connected throughsprings 61a and 61b to a shaft 63 having bearings in each end of acylindrical enclosure 69 forming an arc chamber. As in the formdisclosed in Figs, land 2, arc extinguishing gas pressures may begenerated in this chamber. The bridging member 61 has contacts 16 and 1Iat its ends which cooperate with fixed contacts 12 and 13. In the formshown, three bridging members 61 are connected to the shaft (only onebeing shown) forming a three-pole circuit breaker. The shaft 66 isconnectedfor rotary movement through a predetermined angle such as bymeans oi' a pair` oiylinks 14 and'16 'at each end to an operatingsh'att16 parallel therewith and outside ot the chamber formed by the enclosure89. T'his shaft 18 is connected by means of a link 11 having one endrigidly secured to the shaft 16. and a link 18 pivoted on the other end.of the link 11 to the left-hand end of a iioating operating member 19, apivota1 connection being provided between the link 18 and the operatingmember 19.

This oating member 19 may conveniently be formed as two members orplates secured together in parallel relation and spaced suiciently farapart to receive between them the link 18 and also, at their other ends,a roller which rides on an upright guide member 8|. The righthand end ofthe floating member 19 is biased to its lowermost position shown in Fig.3 by a pair of springs 82, only one of which is shown, one on each side.Also rigidly secured to the iioating member 19 is a latching hook 83which is adapted to engage a roller 84 on the lower end of a trip armpivoted at the point 86 and biased by the weight of its right-handportion in a clockwise direction.

As shown in Fig. 3 the circuit breaker is in its open circuit positionwith the operating handle 81 in its right-hand position. In thisposition a pin 88 carried b-y the member 89 to which the handle issecured, engages an inclined face on the lower end of the floatingmember 19. The member 89 is pivoted on the shaft 16, and, as shown, isin two parallel spaced parts. handle 81 is moved toward the left, thepin 88 engages the inclined surface 90 and moves the floating member 19upward against the force applied thereto by the springs 82, theinclination of the surface 90 at an acute angle with the guide 8| beingsuch that a wedging action and component of forces is produced such thatthe floating member 19 is raised at its right-hand end against the forceapplied by the spring, although the left-hand end may be lifted to acertain extent but not enough to move the bridging contact 61 to itsclosed circuit position. During this movement the roller 80 bearsagainst its guide 8| and rides up the guide.

Whenthe handle 81 reaches its left-hand position, the latching hook 83has moved up past' the roller 84, the lever 85 moving about its pivot ina counterclockwise direction to permit this and the roller 84 has beenmoved by the overbalanced weight of the lever 85 under the hook 83 tohold the hook. The handle 81 may now be released and the springs 82 willthereupon move the floating member 19 in a clockwise direction about theroller 84 as a pivot thereby still further raising the left-hand end ofthe member and moving the bridging c`ontact into engagement with thestationary contacts.

In this position of the iioating member the pin 88 is opposite a notchor recess 9| in the lower side of the floating member 19. With theswitch thus closed if the handle 81 should be moved back toward the leftthe pin 88 moves into the recess 9| having no eiect on the floatingmember. This recess is furthermore deep enough to permit the oatingmember 19 to move downward sufficiently to move the switch arm to itsopen circuit position without engaging the pin 88. Therefore, thisrecess 9| makes it impossible to hold the circuit breaker in its closedposition by means of the handle and the circuit breaker is thereforetrip free of the handle.

Cooperating with the arm 85 is current responsive tripping means foropening the circuit breaker in response to a predetermined currenttherethrough. This means comprises three U shaped bimetallic thermostats92, 92a and 92h included in the respective circuits of the circuitbreaker so as.to be heated by the current. On the upper end of each is abutton or knob 93 (only one of which is shown) made of suitableinsulating material adjustable to vary the current setting. These knobsare adapted to engage a cross bar 93a, the upper endof a lever 94pivoted at a point 95 and having its lower end connected to a link 96connected to theupper 7 end of another pivoted link 91. The upper end ofthe link 91 is connected through a tension spring 98 to the upper end ofa strip member 99 pivoted on a pin |00 and having a projection |0| justbeneath the end of the trip lever 85.

As shown, the spring 98 is just to the left of the pivot |00; thereforethe member 99 is biased to the position shown in a counterclockwisedirection, suitable stops (not shown) being provided to limit itsmovement. Upon the occurence of a predetermined overload the upper endof one or more of the thermostats moves toward the left so that thebutton 93 moves the arm 94 and thereby the upper end of the link 91toward the right whereby the spring 98 is carried to the right-hand sideof the pivot |00. -This sets up a component in a clockwise directionwhereby the member 99 is turned in that direction with a snap action andthe projection |0| caused to i move the arm 85 upward and thereby movethe 'roller 84 to the right out of engagement with the hook 83. Thefloating member 19 is thereupon moved by the springs 82 in acounterclockwise direction about the roller 80 which rests in theinclined guide .|05 to the position shown in Fig. 3 thereby opening thecircuit breaker.

Moreover,.the pivot pin |02 of the roller 84 is extended into the pathof the member 89 so that the member 89 in the position shown in Fig.

3 engages the pin. Therefore, a slight movement y of the handle totheright to its extreme righthand position pushes the roller 84 out fromunder the hook 83, thus permitting the circuit breaker to open with asnap action.

Also the member 89 is provided with an ex- Vinclined surface |04 andthereby moving the floating member slightly counterclockwise and bodilyto the left, the roller 80 riding upward in the inclined guide |05secured to the guide 8|.

When the pin 88 passes downward out of the notch the floating membermoves to the'right in accordance with the bias of the springs 82,

the feuer an moving back down the guide los.

While I have shown a particular embodiment of my invention, it will beunderstood, of course,

that I do not wish to be limited thereto since many modifications may bemade, and I, therefore, contemplate by the appended claims to cover anysuch modifications as fall within the true spirit and scope of myinvention.

What I claim as new and desire to secure by Letters Patent of' theUnited States is:

l. A circuit breaker comprising a oating actuating member, a movablecontact connected to one end of said actuating member, a spring forbiasing the other end of said member for movement in a predetermineddirection, a guide for said other end extending in said predetermineddirection, an intermediate portion of said member being provided with anoperating surface extending at an acute angle with said guide, currentresponsive latching means for pivotally securing said actuating memberat an intermediate point, an operating member provided with a projectionengaging said operating surface to thereby move said actuating memberbodily against the tension of said spring to a position to be secured bysaid latching means, whereby upon release of said operating means saidactuating member` is moved by said spring to actuate said contact to aclosed circuit position.

2. A circuit breaker comprising a floating actuating member, a movablecontact connected to one end of said actuating member, a roller on theother end of said member, a spring for biasing said other end of saidmember for movement 1n a predetermined direction, a guide for saidroller extending in said predetermined direction, an intermediateportion of said member v being provided with an operating surfaceextending at an acute angle with said guide, current responsive latchingmeans for pivotally securing an intermediate portion of said actuatingmember, a pivoted operating member provided with a projection engagingsaid surface upon pivotal movement of said operating member in apredetermined direction to therebymove said actuating member bodilyagainst the tension of said spring to a position to be secured by saidlatching means, whereby upon release of said operating means saidactuating member is moved by said spring to actuate said contact to aclosed circuit position and to disengage said inclined portion from saidprojection, and means operated by. said operating member for releasingsaid latching means.

3. In a circuit interrupter, a pair of contacts one of which is movable,an actuating member for moving said movable contact between open andclosed circuit positions, means releasably retaining one point of saidactuating member in a iixed position serving as a pivot point aboutwhich said actuating member is rotatable to a closed circuit position, aspring applying a biasing force to move said actuating member to saidclosed circuit position and at the same time biasing said point on said.actuating member to move upon release of said retaining means and movethe movable contact toward open circuit position, a guide for saidactuating member, said actuating member being provided with an operatingsurface extending at an acute angle with said guide, and an operatingmember cooperating with said operating surface.

4. In a circuit interrupter, a pair of contacts one of which is movable,an actuating member for moving said movable contact between open andclosed circuit positions, holding means releasably `retaining one pointof said actuating member in a xed position serving as a pivot pointabout which said actuating member is rotatable to a closed circuitposition, a spring applying a biasing force to move said actuatingmember to said closed circuit position and at the same time biasing saidpoint on said actuating member to move upon release of said retainingmeans and move the movable contact toward open circuit position, a guidefor said actuating member spaced from the line of action of the forceapplied by said spring, said actuating mem.. ber being provided with anoperating surface on the opposite side of said line of action from saidguide and extending at an acute angle with said guide, and an operatingmember cooperating with said operating surface to move said actuatingmember against the tension of said spring to a position to be secured bysaid holding means, and means operated by said operating member foractuating said holding means to release said actuating member.

5. In a circuit interrupter, a pair of contacts one of which is movable,an actuating member for moving said movable contact between open andclosed circuit positions, means releasably retaining one point of saidactuating member in a xed position serving as a pivot point about whichsaid actuating member is rotatable to a closed circuit position, aspring applying a biasing force to move said actuating member to saidclosed circuit position and at the same time biasing said point on saidactuating member to move upon release of said retaining means and movethe movable contact toward open circuit position, a guide for saidactuating member spaced from the line of action of the force applied bysaid spring, said actuating member being provided with an operatingsurface extending at an acute angle with said guide, and an operatingmember cooperating with said operating surface, said actuating memberbeing provided with a recess adjacent said operating surface for re-`ceiving said operating member when said actuating member is in a closedcircuit position.

6. A circuit breaker comprising an actuating member, a movable contactconnected to one end of said actuating member, a spring for biasing theother end of said member for movement in a predetermined direction, aguide for said other end, said member being provided with anintermediate operating surface extending at an acute angle with saidguide, current responsive latching means for pivotally securing saidactuating member at an intermediate point, and an operating memberengaging said operating surface to move said actuating member againstthe tension of said spring to a position to be secured by said,

ing means for pivotally securing said actuating member at anintermediate point, an operating member provided with a projectionengaging said operating surface to thereby move said actuating memberagainst the tension of said spring to a position to be secured by saidlatching means, said actuating member being provided with a recessadjacent said operating surface for receiving said projection when saidactuating member is in a I closed circuit position.

LUDWIG S. WALLE.

